Improvement(?)

Thank you very much for this addon, it really makes with importing Blender models into Unity a lot easier!

While all the individual object’s positions and rotations are correct, it seems like I still need to rotate the whole model by 180° on the Y-axis in Unity to make it face in the right direction.

So I tried making a fix for it (the comments in the code should hopefully be self explanatory, although I am not 100% sure about why some of my code segments seem to be required for it to work correctly). Maybe there is a better way, but this seems to work in all scenarios I tested (including more than one child object).

This is the code starting from line 130. I have also attached the full file below (although as .txt, as .py files are not supported for uploading in this case):

# Reset parent's inverse so we can work with local transform directly
		reset_parent_inverse(ob)

		# Create a copy of the local matrix and set a X-90/Z-180 matrix
		mat_original = ob.matrix_local.copy()		
		
		rot_x = mathutils.Matrix.Rotation(math.radians(-90.0), 4, 'X')
		rot_z = mathutils.Matrix.Rotation(math.radians(-180.0), 4, 'Z')
		
		ob.matrix_local = rot_x @ rot_z	
		
		# Apply the rotation to the object
		apply_rotation(ob)
		
		if (ob.parent):
			# Reapply the previous local transform with an X+90 and Y+180 rotation
			ob.matrix_local = mat_original @ mathutils.Matrix.Rotation(math.radians(90.0), 4, 'X') @ mathutils.Matrix.Rotation(math.radians(180.0), 4, 'Y')
		else:
			# Reapply the previous local transform with only an X+90 rotation
			ob.matrix_local = mat_original @ mathutils.Matrix.Rotation(math.radians(90.0), 4, 'X')
			
			# Correct position by inverting X and Y values
			loc_or = ob.location		
			ob.location = (-loc_or.x, -loc_or.y, loc_or.z)
			
			# Correct rotation by inverting Y value
			rot_or = ob.rotation_euler
			ob.rotation_euler = (rot_or.x, -rot_or.y, rot_or.z)

Hope this helps and of course please let me know if you have any suggestions or if there might be a better way!

blender-to-unity-fbx-exporter.txt

[Kai764]

Thank you for this graph, I didn’t know the coordinate systems were that arbitrary…

Personally, Z forward, Y up and X right makes the most sense to me, like Unity or DirectX have it. Unreal also seems good enugh to me, just with Y forward and Z up. But for the rest it looks a bit unintuitive to be honest.

I guess you have to make the best out of it, and at least your addon will work without any problems then.

[EdyJ]

Pretty much every 3D software out here arbitrarily chooses their coordinate system and the meaning of each axis. Here’s an (incomplete) example: